1. Field of the Invention
This invention relates to cameras selectively capable of manual exposure control mode and shutter priority automatic exposure control mode (hereinafter referred to as "TV-AE" mode), and more particularly to a single lens reflex cameras with the aperture value display being made to be presented by using an exposure meter pointer and a follow-up mark in the finder.
2. Description of the Prior Art
With the single lens reflex camera when switched to the manual exposure control mode, two light metering aspects becomes possible, one of which operates at the full open aperture of the diaphragm in the used interchangeable lens mounting, and another aspect which operates with the stopping down to a desired aperture value. The photographer has the choice of these two aspects and will determine which one of the aspects is to be used depending upon his aim to shoot. Hereinbelow these light metering aspects will be described in.
The aforesaid light metering-at-open aperture aspect is a system in which a follow-up mark representing the actual aperture value of the diaphragm in the photographic objective lens mounting attached to the camera is manually adjusted to coincidence with a meter pointer of which the deflected position represents a correct exposure, i.e., aperture value, thereby the correct exposure is obtained. On the other hand, the aforesaid light metering-at-preset aperture aspect is a system in which, whilst the objective lens is stopped down manually, the meter pointer which is left to appear in the field of view of the finder is placed in registry with a null point by turning the shutter dial or the diaphragm ring, thereby the correct exposure is obtained. It is to be noted here that, in the latter system, the follow-up mark is taken out of the field of view of the finder.
When such manual exposure control camera having the aforesaid follow-up mark operatively connected to the diaphragm mechanism is made to have built therein a shutter priority automatic exposure control mechanism, it can be said in common to both the aforesaid light metering aspects that the information display in the finder becomes very annoying, since the follow-up mark is caused to move from the start position of the adjustment of the diaphragm in the objective lens to a setting position for the correct exposure in response to the diaphragm adjusting operation of the objective lens each time a shutter release operation is carried out. Further, the use of a motor drive or auto-winder on the camera leads to move the follow-up mark vibrationally as the camera operates at a high speed, thereby giving rise to a problem of shortening the life-time.